Method and apparatus for improving images provided by spatial light modulated (SLM) display systems

ABSTRACT

The invention provides a method and system for reducing distortion in images provided by display systems employing Spatial Light Modulating elements is provided. A method comprises steps of providing a set of pixel values corresponding to pixels of an image to be displayed. The number of pixel values comprising the set is greater than the number of available SLM elements. At least some of the pixel values are adjusted to provide a set of adjusted pixel values. At least a first set of pixels and a second set of pixels are generated from the set of adjusted pixel values. The image is displaying as a matrix of pixels comprising the first set of pixels and the second set of pixels. At least one of the pixels of the first set overlaps at least one of the pixels of the second set and the adjusting step is carried out by adjusting pixel values of the pixel data set to compensate for image distortion due to overlapping pixels of the matrix.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit, under 35 U.S.C. § 365 ofInternational Application PCT/US2005/009621, filed Mar. 22, 2005, whichwas published in accordance with PCT Article 21(2) on Oct. 6, 2005 inEnglish and which claims the benefit of U.S. provisional patentapplication No. 60/555,253 filed Mar. 22, 2004.

FIELD OF THE INVENTION

The present invention generally relates to Spatial Light Modulation(SLM) display systems, and in particular to filters and filter methodsfor use in SLM systems.

BACKGROUND OF THE INVENTION

Spatial Light Modulating (SLM) systems include Digital Light Processing™(DLP™) systems. DMD and DLP™ are trademarks of Texas InstrumentsCorporation. Recent developments in SLM technology rely on SLM elementsthat provide diamond shaped pixels instead of square shaped pixels.Processing techniques for SLM systems include a so called “smooth pixel”processing technique. According to the smooth pixel technique, adisplayed image is formed by combining a first set of pixels with asecond set of pixels. The second set is displaced from the first set.The combined first and second pixel sets form a displayed image.

In one example SLM system, an SLM array comprising a number of SLMelements provides first and second pixel sets for each incoming picture,or frame, to be displayed. The combined pixels from the first and secondpixel sets provide more displayed pixels than the number of SLM elementsemployed to provide the pixel sets.

However, a drawback is associated with this technique. Pixels of thefirst and second pixel sets overlap in the displayed image. At leastsome of the pixels from the first set effectively overlap at least someof the pixels from the second set. As a result, when the pixel sets aredisplayed together so as to form an image, light in the regions ofoverlapping pixels is a combination of light from each of theoverlapping pixels. This sometimes results in brighter than intended, orless bright than intended image portions.

Thus, some loss of image quality is incurred with this technique ascompared to other display techniques. Accordingly, image processingdevices and methods are needed that account for distortion due tooverlapping pixels in displayed pixel sets of SLM devices.

SUMMARY OF THE INVENTION

According to various embodiments of the invention methods and systemsfor reducing distortion in images provided by display systems (100)employing Spatial Light Modulating (SLM) elements are provided. A methodaccording to one embodiment of the invention comprises steps ofproviding a set (620) of pixel values corresponding to pixels of animage to be displayed. The number of pixel values comprising the set isgreater than the number of available SLM elements. At least some of thepixel values are adjusted to provide a set of adjusted pixel values(678). At least a first set of pixels and a second set of pixels aregenerated from the set of adjusted pixel values. The image is displayedas a matrix of pixels (450) comprising the first set of pixels (410) andthe second set of pixels (430). At least one of the pixels of the firstset overlaps at least one of the pixels of the second set and theadjusting step is carried out by adjusting pixel values of the set ofpixel values to compensate for image distortion due to overlappingpixels of the matrix.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be described below in moredetail, with reference to the accompanying drawings, in which:

FIG. 1 is a block diagram illustrating a display system including anarray of spatial light modulation (SLM) elements suitable forimplementing various embodiments of the invention.

FIG. 2 is a block diagram illustrating in more detail the electronicssubsystem of the display system illustrated in FIG. 1.

FIG. 3 is a block diagram illustrating an SLM system including a pixelfilter according to an embodiment of the invention.

FIG. 4 is a diagram illustrating relationship between received pixeldata, adjusted pixel data and a pixel matrix according to an embodimentof the invention.

FIG. 5 is a block diagram of a pixel filter according to an embodimentof the invention.

FIG. 6 illustrates an example lookup table suitable for use in the pixeldata filter of FIG. 5 according to an embodiment of the invention.

FIG. 7 is a detailed diagram of an embodiment of the pixel dataprocessing device illustrated in FIG. 5.

DETAILED DESCRIPTION

Spatial Light Modulator (SLM) devices find increasing use in a widerange of imaging applications such as video image projection andprinting. Typical spatial light modulators include devices such asLiquid Crystal Devices (LCDs) and digital micro-mirror devices (DMDs™).A typical spatial light modulator comprises a two-dimensional array ofmodulator elements that operate upon incident light in order to form atwo-dimensional image on a display surface. LCD based devices use lightpolarization characteristics in order to modulate each light element inthe array. DMD™ based devices use an array of tiny micro-mirrors tomodulate individual light elements. Each element in a spatial lightmodulator array exhibits a variable light intensity in response to acorresponding drive voltage level. In one embodiment of the invention,each element in an SLM array corresponds to at least one pixel of adisplayed image.

FIG. 1 is a pictorial diagram illustrating an example system 100including a Spatial Light Modulating (SLM) array 500 suitable forimplementing various embodiments of the present invention. System 100comprises at least one light source 301 coupled to an optical system400. Optical system 400 comprises relay and illumination optics 300 andprojection optics 200. Optical system 400 includes at least one array500 of spatial light modulating elements 502. According to an embodimentof the invention array 500 comprises a semiconductor-based array ofreflective light elements 502. According to one embodiment of theinvention, SLM array 500 comprises a binary Pulse Width Modulated (PWM)array 500 of light switching elements 502. In one embodiment, elements502 of PWM array 500 comprise micro-electromechanical system (MEMS)devices, for example, mirrors of a Digital Micromirror Device™ (DMD)™.

An electronics subsystem 600 includes an input for receiving a videosignal 601 and an output coupled to the SLM array 500. Electronicssubsystem 600 processes incoming video signal 601 so as to provide PWMsignals to drive elements 502 of array 500. The PWM signals control theangle and dwell time of elements 502 of array 500 in accordance withpixel values provided by video signal 601. Properties, for example,brightness, of pixels displayed on display screen 499 are related to thedwell time of respective corresponding micro-mirror elements 502.

Electronics subsystem 600 receives a video signal 601 from a source ofvideo signals (not shown). Video signal 601 comprises video image datacorresponding to video images to be projected and displayed on displaydevice 499. Electronics subsystem 600 processes video signal 601 andprovides a processed video signal 602 to drive array 500.

Optics system 400 comprises at least one relay and illumination opticsportion 300, at least one projection optics portion 200 and at least onelight source 301. Light from light source 301 is transmitted through atleast one relay optics portion 300. Light from relay optics portion 300is projected onto light reflecting elements 502 of SLM array 500.

According to embodiments of the invention, video signal 601 is providedby at least one of a wide variety of suitable video signal sources.Suitable video signal sources include for various embodiments of theinvention are too numerous to recite in total. However, some examplesinclude, but are not limited to, digital versatile disk (DVD) systems,set top boxes, broadcast video sources, Internet video sources, cablevideo sources, satellite video sources, wireless and telephonic sources,to name but a few. Embodiments of the invention comprise digital videointermediate systems wherein video sources include film, telecines,video masters and the like.

Regardless of video signal source, suitable video signals 601 forembodiments of the invention include, among others, analog videosignals, digital video signals, component video signals and compositevideo signals. Suitable signal formats include, among others, NationalTelevision Standards Committee (NTSC) format, Phase Alternate Lines(PAL) format, and PAL plus format. Any video format providing pixelvalues corresponding to pixels of an image to be displayed is suitablefor use in various embodiments of the invention.

FIG. 2 illustrates functional blocks of the electronics subsystem 600illustrated in FIG. 1 according to an embodiment of the invention.Electronics subsystem 600 comprises a receiver 610 for receiving videosignal 601. Receiver 610 is coupled to video processing unit 640. Videoprocessing unit 640 is coupled to SLM array driver 690.

According to embodiments of the invention, receiver 610 receives videosignal 601 at an input. In an example embodiment of the invention,receiver 610 decodes video signal 601 and performs Analog to Digital(A/D) conversion, Luminance-chrominance separation (Y/C separation), andchrominance demodulation of video signal 601 in accordance withconventional video signal receiving and decoding techniques,

According to embodiments of the invention, video processing unit 640further provides video processing functions, for example, progressivescan conversion, and resampling of video signal 601 in accordance withconventional techniques. Video processing unit 640 is coupled to an SLMdevice driver 690. SLM device driver 690 provides drive signals fordriving elements 503 of SLM array 500. According to an embodiment of theinvention, video processor provides enhanced Chrominance (2C) andLuminance (2Y) signals for use by driver 690 in driving elements 503 ofarray 500 so as to modulate light in accordance with video signal 601.

Video processing unit 640 includes pixel filter 320 coupled to a pixelgroup generator 680. In one embodiment of the invention, pixel groupgenerator 680 is a conventional device providing pixel groups for socalled, “smooth pixel” processing techniques. According to oneembodiment of the invention, pixel filter 320 is implemented byprogramming a processor of video processing unit 640 so as to implementpixel processing functions in accordance with the various embodiments ofthe invention described herein. In alternative embodiments of theinvention, functions of pixel filter 320 are provided by hardwarewithout the need for programming a processor. Still other embodiments ofthe invention implement some functions of pixel filter 320 in hardwarewhile other functions are implemented by a processor programmed forcarrying out the other functions. However, as those of ordinary skill inthe art will readily appreciate upon reading the specification herein, awide variety of hardware and software combinations will be suitable forimplementing the invention. Therefore, the pixel filter of the inventionis not limited to one specific hardware and processor arrangement.

According to one embodiment of the invention, receiver portion 610provides luminance (Y) signals 620 to pixel filter 320 based upon videosignal 601. According to one embodiment of the invention, receiverportion 610 provides chrominance (C) signals 649 to pixel filter 320based upon video signal 601.

In some embodiments of the invention, video signal processor 640provides further processing functions including, for example, colorspace conversion, gamma correction removal, error diffusion, on screendisplay capability, Red, Green, Blue (RGB) input receiving capability,and user operable image controls. In one embodiment of the invention,driver 690 includes a Field Programmable Gate Array (FPGA).

In one embodiment of the invention Field Programmable Gate Array (FPGA)690 receives RGB video signals from video signal processor 640 andprovides PWM control functions, image reformatting, bit plane conversionand DMD drive signal functions based, at least in part, on the RGB videosignals. According to embodiments of the invention, system 600 furthercomprises memory 622 and timing and control circuits 621 for electronicssubsystem 600.

As will be readily appreciated by those of ordinary skill in the artprocessors are commonly embedded throughout systems in a wide variety ofconfigurations and capabilities. Any processor configurationimplementing the inventive circuits, systems and methods describedherein remain within the scope of the invention.

FIG. 3 is a block diagram illustrating an embodiment of the invention.Display screen 499 is arranged with respect to SLM array 500 so as todisplay an image comprising a matrix 450 of pixels. Matrix 450 comprisesat least a first pixel group 410 and a second pixel group 430. (alsoillustrated in FIG. 4). According to alternative embodiments of theinvention, matrix 450 comprises more than two pixel groups. According toan embodiment of the invention, the number of pixels comprising matrix450 is greater than the number of elements 502 of SLM array 500 used toprovide first and second pixel groups 410 and 430.

As illustrated in FIG. 3, light from a light source 301 is transmittedthrough relay optics subsystem 300. In one embodiment of the invention,optics subsystem 300 includes a means for providing colored light.According to one embodiment of the invention, optics subsystem 300includes a color wheel alternately producing red, green and blue light.According to an alternative embodiment of the invention, light source301 comprises a red light source, a green light source and a blue lightsource. The colored light is projected onto array 500 and reflected fromarray 500. Light reflected from array 500 is provided to display 499 viaprojection optics subsystem 200.

Elements 502 of array 500 are driven in accordance with pixel valuesprovided by pixel data set 620. Each pixel of matrix 450 corresponds toa pixel value of incoming pixel data set 620. Pixel data set 620 isgenerated based upon video signal 601. In FIG. 3 pixel data set 620 isrepresented by an arrangement of letters A through O.

Pixel processor 320 adjusts pixel values of pixel data set 620 andprovides adjusted pixel data set 678 to pixel group generator 675. InFIG. 3 adjusted pixel data set 678 is represented by an arrangement ofletters A′ through O′. Pixel group generator 675 separates adjustedpixel data set 678 into first and second pixel data groups (679 and680). In one embodiment of the invention, pixel group generator 675operates in accordance with a known pixel processing technique such as a“smooth pixel” processing technique. According to smooth pixelprocessing, an input pixel data set, for example, 620 is separated intofirst and second pixel data groups. The first and second pixel datagroups provide first and second pixel groups comprising a displayedmatrix.

However, conventional pixel processing techniques do not include pixelfilter 320, nor do conventional systems provide an adjusted pixel dataset 678 to a pixel generator 675. Accordingly, first and second pixelgroups 410 and 430 comprising matrix 450 according to the inventionprovide significant advantages over conventional smooth pixel processingtechniques.

FIG. 4 illustrates the relationship between pixel data set 620, adjustedpixel data set 678, pixel data groups 679 and 680, pixel groups 410 and430, and pixel matrix 450 according to an embodiment of the invention.As illustrated in FIG. 4, first pixel group 410 comprises rows h andcolumns c of adjacent pixels 412. For convenience, a single indicator412 indicates individual pixels of group 410. Second pixel group 430comprises rows h and columns c of adjacent individual pixels 432.

Pixel groups 410 and 430 are projected onto display screen 499 so as toappear displaced from each other, for example, by a distance d. In oneembodiment of the invention, pixel groups 410 and 430 are displaced fromeach other in a direction substantially in x-direction of the plane ofthe surface of display screen 499.

In one example embodiment of the invention, second pixel group 430 isdisplayed spaced from first pixel group 410 by a distance equal to abouthalf of the height of a single pixel. The resulting pixel matrix 450therefore comprises overlapping pixels. In other words, individualpixels from first pixel group 410, overlap individual pixels from secondpixel group 430.

In one embodiment of the invention, SLM elements 502 comprise diamondshaped elements. Therefore, pixels of matrix 450 comprise substantiallydiamond shaped pixels (example illustrated in FIG. 4). However, otherpixel shapes, e.g. square pixels, are known, and are suitable for someapplications of the invention.

FIG. 3 illustrates an optical element 210 as one example of conventionalmeans for providing the spacing for pixel groups 410 and 430. Opticalelement 210 reflects one of pixel sets 410 and 430 onto screen 499 at afirst angle Ø₁. Optical element 210 subsequently projects the otherpixel set at a second angle Ø₂. This technique has the advantage ofproviding a matrix 450 with more displayed pixels than the number ofavailable elements 502 on SLM device 500. In one embodiment of theinvention, the number of pixels comprising matrix 450 is about twice thenumber of available micro-mirrors 502 of SLM device 500.

However, the technique described above results in overlapping pixels.Light from each of the overlapping pixels combines. Therefore, thedisplayed brightness for a given pixel sometimes fails to correspond tothe brightness value provided in pixel data set 620. In some cases thedisplayed brightness of overlapping pixels is greater than the intendedbrightness. In other cases, the displayed brightness of overlappingpixels is less than the intended brightness.

According to an embodiment of the invention pixel data set 620 isprovided to pixel filter 320. Filter 320 provides modified pixel dataset 678. Pixel data groups 679 and 680 are formed from modified pixeldata set 678. The pixel values of pixels of pixel data groups 679 and680 are used to generate pixel groups 410 and 430 respectively.Displayed combined pixel groups 410 and 430 comprise matrix 450.

In accordance with an embodiment of the invention, pixel filter 320provides adjusted example data set 678 as represented by the followingdiagram:

$\begin{matrix}A^{\prime} & B^{\prime} & C^{\prime} & D^{\prime} & E^{\prime} \\F^{\prime} & G^{\prime} & H^{\prime} & I^{\prime} & J^{\prime} \\K^{\prime} & L^{\prime} & M^{\prime} & N^{\prime} & O^{\prime}\end{matrix}$

First pixel data group 679 comprises pixel data labeled A′, C′, E′, G′,I′, K′, M′, O. Second pixel data group 680 comprises pixels labeled B′,D′, F′, H′, J′, ′L, N′. Pixel groups 410 and 430 are generated based onpixel data groups 679 and 680 respectively. Matrix 410 comprises firstpixel group 410 and second pixel group 430.

As can be seen from the drawing of matrix 450, pixels from the firstpixel group 410 at least partially overlap pixels of pixel group 430 andvice versa. For example, the G pixel position in the first pixel group410 is overlapped by the B, F. L and H pixel positions from the secondpixel group 430. This overlap causes intensity distortion of the imagerepresented by matrix 410.

According to an embodiment of the invention, distortion in pixelintensity caused by the overlap is reduced by an image enhancing filterarrangements 320 illustrated in FIGS. 3, 5 and 7.

FIG. 5 illustrates an embodiment of a pixel filter 320 according to anembodiment of the invention. Pixel filter 320 comprises at least onetwo-dimensional filter that operates on respective pixels of pixel dataset 620 in accordance with an array h given by:

$\begin{matrix}\; & {- \alpha} & \; \\{- \alpha} & \beta & {- \alpha} \\\; & {- \alpha} & \;\end{matrix}$

-   -   wherein β is a scaling factor associated with a pixel of pixel        data set 620 from which the intensity distortion is to be        removed; and    -   α is a scaling factor for pixels overlapping the pixel of pixel        data set 620 from which the intensity distortion is to be        removed.        -   More particularly, filter 320 adjusts intensity values I of            respective pixels of data set 620 by an amount sufficient to            compensate for the intensity contribution of pixels            overlapping a respective pixel in matrix 450. For example,            in FIG. 4, the intensity (I_(G)) of pixel G in pixel data            set 620 is scaled by an amount (β) such that the intensity            distortion caused by overlapping pixels B (I_(B)), F            (I_(F)), L (I_(L)) and H (I_(H)) in displayed matrix 450 is            reduced. In an embodiment of the present invention, adjusted            pixel G′ has an adjusted intensity value I_(G′) in            accordance with the relationship illustrated below:            I _(G′)=β(I _(G))−α(I _(H) +I _(L) +I _(B) +I _(F))  (1)    -   Wherein:    -   β is a scaling factor associated with the pixel G from which the        intensity distortion is to be removed; and    -   α is a scaling factor associated with overlapping pixels that        are contributing to the intensity of pixel G.

According to one embodiment of the invention, a relationship between βand α is given by: β=1+4α. This relationship provides unity DC gain.However, the invention is not limited in this regard. In one embodimentof the invention, α is approximately +⅛ and β is approximately 3/2.Selecting these example scaling factors has been found to provide unityDC gain while compensating for distortion in some embodiments of theinvention.

According to the example above, the pixel data for the example data set620, and the adjusted data set 678 is represented as follows:

$\begin{matrix}A & B & C & D & E \\F & G & H & I & J \\K & L & M & N & O\end{matrix}->\begin{matrix}A^{\prime} & B^{\prime} & C^{\prime} & D^{\prime} & E^{\prime} \\F^{\prime} & G^{\prime} & H^{\prime} & I^{\prime} & J^{\prime} \\K^{\prime} & L^{\prime} & M^{\prime} & N^{\prime} & O^{\prime}\end{matrix}$

FIG. 5 is a block diagram illustrating an example filter arrangement 320representing one of three like filters 320 a, 320 b, 320 c illustratedin FIG. 3. Filter 320 implements the relationship described in equation1 above for each pixel in respective red, green and blue components ofcomponent video signal 620. For convenience, the operation of one filter320 will be described in relation to an example pixel G. Overlappingpixel groups 410 and 430 as shown in FIG. 4 are referred to herein as anexample for purposes of discussion. However, it will be understood thateach of the pixels comprising incoming pixel set 620 are suitable forprocessing in the same way to remove intensity distortion caused byoverlapping pixels.

Referring to FIG. 5, a pixel filter 320 according to an embodiment ofthe invention is illustrated. Pixel filter 320 comprises a delay circuit646. Delay circuit 646 receives pixel data of pixel data set 620. Delaycircuit 646 delays the received pixel data so as to provide pixel datafor a plurality of pixels substantially simultaneously. In the exampleillustrated in FIG. 5, delay circuit 646 provides pixel data for pixelsH, L, F and B (overlapping example pixel G in matrix 450.) to adder 648.At the same time, delay circuit 646 provides data for example pixel G toa second scaler 652. Adder 648 provides an output representative of thesum of pixel values for pixels H, L, F and B to a first scaler 651.First scaler 651 applies a scaling factor α to its input to provide ascaled output. Second scaler 652 applies a scaling factor β to its inputto provide a scaled output. The scaled outputs of scalers 651 and 652are combined by subtractor 653. The difference output of subtractor 653represents an adjusted value G′ for example pixel G. According to oneembodiment of the invention, the difference output of subtractor 653 isoptionally provided to a limiter. In that case, successive output valuesprovided by limiter 654 comprise adjusted pixel data set 678.

According to one embodiment of the invention, a scaling factor for firstscaler 655 is adjustable by an adjustment factor X provided by firstadjuster, 655. According to one embodiment of the invention, a scalingfactor for the second scaler 652 is adjustable by an adjustment factor Yprovided by second adjuster 657.

FIG. 6 illustrates a pixel filter control circuit 700 for implementingan embodiment of pixel filter 320 including adjustable scaling factors.Filter control circuit 700 comprises a look up table 150. Look up table150 stores a plurality of selectable XY pairs of adjustment factors forX 154 and Y 156. Each XY pair of the table corresponds to one of thefilter control setting 152 of table 150. In the example illustrated inFIG. 6, eight possible filter control settings, e.g., 0 through 8 areprovided. To select scaler adjustment factors X and Y a filter controlsignal representing one of the eight control settings is provided atfilter control input 688 of table 150, The XY value pair correspondingto the filter control setting selected by input 688 provides adjustmentfactors X and Y to first and second adjusters 655 and 657. In thatmanner, lookup table 150 provides adjustable scaling factors for scalers655 and 652.

In one embodiment of the invention, the X and Y values of table 150maintain a given relationship between scaling factors α and β whilepermitting adjustment of scaling factors α and β. In one embodiment ofthe invention, the given relationship between α and β is a unity gainrelationship given by:β=1+α.

FIG. 7 is a more detailed diagram of one embodiment of the filterillustrated in FIG. 6. A video signal representing pixel data set 620 isprovided to full line delay registers 803 and 805. Line delay registers803 and 805 delay the video signal by an entire line of displayed videoaccording to one embodiment of the invention. For the purpose of thepresent example, the delays of line delay registers 803 and 805 arechosen according to the principles illustrated by the following example.When the data for pixel M, for example, is presented at input 620, theoutput of line delay register 805 will be H and the output of line delayregister 803 will be C. As illustrated in FIG. 7, the output of linedelay registers 805, 803 and the original video input signal, e.g., Mare coupled respectively to a second bank of delay registers 807, 809,and 800. The outputs of delay registers 803 and 800 are added by adder812. The output of adder 812 is provided to a first input of adder 823.

A second input to adder 823 is provided as follows. An output of delayelement 809 is provided to delay element 811. The output of delayelement 811 is provided to one input of adder 813. The other input toadder 813 is provided by the output of delay element 807. A sum outputof adder 813 is coupled to the second input to adder 823.

According to the example above, the sum H+L+B+F is provided. Pixels H,L, B and F are pixels overlapping pixel G in matrix 450 of FIG. 1. Thissum represents a sum of pixel intensity values for each of the pixelsthat overlap pixel G. The sum H+L+B+F is then scaled by a scaling factorα. Scaling is accomplished in one embodiment of the invention asfollows. The sum H+L+B+F is provided to multiplier 814. Multiplier 814multiplies the sum H+L+B+F accordance with a first multiplier X,indicated at multiplier input 655. The output of multiplier 655 isprovided to divider 651. In the embodiment illustrated In FIG. 7 divider651 divides the output or multiplier 655 by 32. Therefore, the sum(H+L+B+H) output from adder 823 is scaled by a factor of x/32, where 32is a constant and x/32 comprises scaling factor α. For example if x=4 inFIG. 7, then a= 4/32 or ⅛. Accordingly, the scaled sum for pixels in theexample above is (⅛) (H+L+B+F).

Similarly, a second scaling factor β is applied to pixel data value G byproviding data value G to multiplier 804. The output of multiplier 804is provided to a ⅛ divider 652. Therefore, G is scaled by a factor ofy/8 comprising scaling factor β. A subtractor 817 provides an outputrepresenting the difference between the scaled pixel intensity datavalue β(G) and the scaled sum of the intensity values of overlappingpixels, i.e., (α) (H+L+B+F).

In one embodiment of the invention the output of subtractor 817 isprovided to a limiter 654. Limiter 654 maintains the difference valueprovided by subtractor 817 within a range of pixel intensity values.According to one embodiment of the invention, various additional delayregisters, e.g., 819 are provided in the filter circuit in FIG. 7 toallow for circuit settling times.

It will be appreciated by those of ordinary skill in the art thatvarious other relationships between β and α, e.g., other than unity gainrelationships, are possible. Table 600 is suitable for implementing awide variety of relationships. The other relationships can readily beaccomplished by substituting appropriate values of x y pairs in table600. Advantageously the pairs are customizable such that a specificrelationship is maintained between β and α for all values of x and ypairs on the table.

According to one embodiment of the invention, look up table 150 isimplemented in a memory (not shown), for example, a semiconductormemory. In that case, the memory stores values of x and y. The memoryincludes x and y outputs coupled to inputs x (indicated at 655) and y(indicated at 657) respectively of filter 645 of FIG. 7. In a look uptable embodiment comprising eight x,y pairs, x is selectable such that αranges in 1/32 increments between 0 to 7/32. For the same table, y isselectable such that β ranges from 1 to 15/8 in increments of ⅛.

Those skilled in the art will readily appreciate that the foregoingfilters are capable of implementation in various combinations ofsoftware, hardware and/or firmware. According to one embodiment of theinvention, look up table values are stored in an electronic memory. Forexample, data sets can be stored in a bus register, RAM or other datastorage device associated with a DLP system microprocessor. Still, theinvention is not limited in regard to memory types, and other suitablemethods exist for storing such values. In one embodiment of theinvention, filter control values are selectable by a user via a useroperable interface with a DLP display system. According to anotherembodiment of the invention, filter control values are automaticallyadjusted by a system microprocessor (not shown) provided for controllingthe DLP system.

Further, while FIGS. 5 and 7 represent embodiments of filters accordingto the invention, those skilled in the art will recognize that theinvention is not limited to particular component arrangements. Forexample, other filter architectures are possible for implementing theinvention. That is, other filter architectures are suitable foroperating on pixel values so as to adjust pixel intensity to at leastpartially compensate for the intensity distortion caused by overlappingpixels. Further, while it is be advantageous in many embodiments of theinvention to select β=1+4α, the invention is not limited in this regardto such values. The values of β and α are selectable to have othervalues and relationships according to various embodiments of theinvention.

1. A method for reducing distortion in images provided by a display system employing an array of individual pixel elements in a Spatial Light Modulator comprising the steps of: providing a set of pixel values corresponding to pixels of an image to be displayed wherein the number of pixel values comprising said set is greater than the number of available SLM elements; adjusting at least some of said pixel values to provide a set of adjusted pixel values; generating at least a first set of pixels and a second set of pixels from said set of adjusted pixel values; transmitting light from a relay optics portion onto micromirror elements containing adjusted first and second pixel group sets; reflecting said transmitted light containing said adjusted first and second pixel sets off an optical element at varying angles to provide spacing between said pixel group set when projected onto a display screen; displaying said image on said display screen as a matrix of pixels comprising said first set of pixels and said second set of pixels, wherein the number of pixels of said matrix is greater than the number of said SLM elements, and wherein at least one of the pixels of said first set overlaps at least one of the pixels of said second set; wherein said adjusting step is carried out by adjusting pixel values of said set of pixel values to compensate for image distortion due to overlapping pixels of said matrix; wherein said adjusting step includes a step of scaling a first respective pixel value of said set of pixel values in accordance with a first scaling factor β, summing values of pixels overlapping said first respective pixel values and scaling the sum by a second scaling factor, α, and subsequent to said scaling step, subtracting said first respective pixel value from said summed pixel values to determine an adjusted value of said first respective pixel value.
 2. The method of claim 1 wherein said set of pixel values comprises luminance values.
 3. The method of claim 1 wherein said set of pixel values comprises chrominance values.
 4. The method of claim 1 wherein said first scaling factor is adjustable.
 5. The method of claim 1 wherein said second scaling factor is adjustable.
 6. The method of claim 1 wherein said first scaling and second scaling factors are related according to the equation: β=1+4α.
 7. A system employing an array of individual pixel elements in a Spatial Light Modulator to display video images comprising: a source of video image data comprising at least one set of pixel values corresponding to pixels of an image to be displayed wherein the number of pixel values in said at least one set is greater than the number of individual pixel elements in said SLM, said at least one set of pixel values further comprising a respective pixel value and a plurality of pixel values corresponding to pixels that overlap a respective pixel having said respective pixel value; a pixel processor further comprising a filter, said filter coupled to said source to receive said at least one set of pixel values, said filter configured to adjust at least one pixel value in said set to provide an adjusted set of pixel values said filter includes at least one of a first scaling factor for scaling said respective pixel value and a second scaling factor for scaling said plurality of pixel values that overlap said respective pixel value; a pixel group generator coupled to said filter to receive said adjusted set of pixel values, said pixel group generator providing at least a first group of pixels and a second group of pixels based upon said adjusted set of pixel values; a relay optics portion configured for transmitting light onto micromirror elements containing an adjusted first pixel data group and an adjusted second pixel data group; an optical element configured for reflecting at varying angles said transmitted light containing said adjusted first pixel data group and said adjusted second pixel data group to provide spacing between said adjusted first and second pixel groups when said adjusted pixel groups are projected onto a display screen; wherein said individual pixel elements in said SLM cooperate with said pixel group generator to display said image as a matrix of pixels comprising said first group of pixels and said second group of pixels, wherein at least one of the pixels of said first group overlaps at least one of the pixels of said second group in said matrix; wherein said filter is configured to adjust pixel values of overlapping pixels to compensate for image distortion due to said overlapping pixels.
 8. The system according to claim 7 wherein at least one of said first and second scaling factors is adjustable.
 9. The system according to claim 7, wherein said pixels comprise diamond shape pixels.
 10. The system according to claim 7, wherein said filter is further comprised of an adder configured for summing said plurality of pixel values corresponding to pixels that overlap said respective pixel value.
 11. The system according to claim 10, wherein said filter is further comprised of a subtractor for subtracting said first respective scaled pixel value from said summed scaled pixel values to determine an adjusted value of said first respective pixel value. 